Learn how to design scalable Select Channels Go concurrent programming in golang

Learn how to design scalable Select Channels Go concurrent programming in golang

Introduction:

The Go language is an efficient and concise A concurrent programming language whose concurrency model is mainly based on goroutine and channel. Through the intuitive communication mechanism of goroutines' lightweight threads and channels, the concurrent programming model of the Go language provides an efficient way to handle concurrent tasks.

In the Go language, it is common to use channels for communication. In addition to the basic usage of channels, we can also use the select statement to handle the selection and communication of multiple channels to achieve more flexible and scalable concurrent programming.

This article will take a case as an example to introduce how to use select statements and channels to design a scalable concurrent program.

Case:

We assume that there is a task distributor, and multiple worker threads obtain tasks from the task distributor for processing. The task dispatcher dynamically adjusts the task allocation strategy based on the length of the task queue and the number of worker threads.

First, we define a task structure Task:

type Task struct {
    ID    int
    Value int
}

Next, we create a task distributor Dispatcher and implement related methods:

type Dispatcher struct {
    workerCount  int
    taskQueue    chan Task
    workerDone   chan struct{}
    workerFinish chan struct{}
}

func NewDispatcher(workerCount int) *Dispatcher {
    return &Dispatcher{
        workerCount:  workerCount,
        taskQueue:    make(chan Task),
        workerDone:   make(chan struct{}, workerCount),
        workerFinish: make(chan struct{}),
    }
}

func (d *Dispatcher) Start() {
    for i := 0; i < d.workerCount; i++ {
        go d.worker()
    }

    go d.adjust()
}

func (d *Dispatcher) worker() {
    for task := range d.taskQueue {
        // 处理任务
        fmt.Printf("Worker[%d] processing task %d
", task.ID, task.Value)
        time.Sleep(1 * time.Second)
        d.workerDone <- struct{}{}
    }
}

func (d *Dispatcher) adjust() {
    for {
        select {
        case <-d.workerFinish:
            d.workerCount--
            if d.workerCount == 0 {
                return
            }
        case <-time.After(5 * time.Second):
            if len(d.taskQueue) > 10 && d.workerCount < 5 {
                d.workerCount++
                go d.worker()
            }
        }
    }
}

func (d *Dispatcher) Dispatch(task Task) {
    d.taskQueue <- task
}

func (d *Dispatcher) Wait() {
    for i := 0; i < d.workerCount; i++ {
        <-d.workerDone
    }
    close(d.taskQueue)
    close(d.workerFinish)
    close(d.workerDone)
}

In Dispatcher we Four channels are defined: taskQueue is used for task reception and distribution, workerDone is used for return of task completion signals, and workerFinish is used for counting and adjusting worker threads.

The Start method is used to start the worker thread and the task adjustment thread, where the worker method is the specific implementation of the worker thread. Each worker thread takes out the task from the taskQueue for processing, and sends the task completion signal to workerDone.

The adjust method is the specific implementation of the task adjustment thread. It uses select to monitor two channels. When workerFinish receives the signal, it means that a worker thread has completed the task and personnel adjustments need to be made. When the time.After timer triggers, it means that the task queue length is too long and worker threads need to be added to handle more tasks. By dynamically adjusting the number of worker threads, we can make full use of system resources and keep tasks processed quickly.

The Dispatch method is used to submit tasks to the task distributor. The Wait method is used to wait for the completion of all tasks.

Usage example:

func main() {
    dispatcher := NewDispatcher(3)
    dispatcher.Start()
    
    for i := 0; i < 20; i++ {
        task := Task{
            ID:    i,
            Value: i,
        }
        dispatcher.Dispatch(task)
    }
    
    dispatcher.Wait()
}

In this example, we create a Dispatcher and start 3 worker threads. Then, we distributed 20 tasks to the Dispatcher. Finally, wait for the completion of all tasks through the Wait method.

Summary:

By using select statements and channels, we can flexibly design scalable concurrent programs. In this case, we show how to use select and channel to implement a task dispatcher that dynamically adjusts the task distribution strategy. By using this method, we can make full use of system resources and keep tasks processed quickly.

In actual concurrent programming, we can further expand and optimize this model according to specific needs and scenarios. I hope this article can help readers better understand and use select and channels to design scalable Go concurrent programs.

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